Recently, secondary batteries such as a high performance lithium battery for small electronic devices such as a handheld terminal and a mobile electronic device, fixed devices such as a small electric power storage device for home use, moving devices such as an electric motorcycle, an electric automobile, a hybrid electric automobile, and the like have become in demand more and more. Therefore, batteries having high capacity, but small size and light weight are desired and batteries having stable performance in various environments are also desired.
Therefore, among a lithium-ion secondary battery, a polymer battery utilizing polymer electrolyte (polyelectrolyte) constituted of polymer instead for electrolyte impregnated into microporous membrane has attracted an attention. Since a gelled electrolyte having liquid electrolytic solution impregnated into polymer macromolecule, the electrolytic solution is retained in the polymer macromolecule such that there is an advantage to improve the stability of the battery performance and to have higher flexibility to shape the battery. However, the polymer electrolyte has less mechanical strength. And the polymer electrolyte may be broken so as to cause a short circuit formed between the negative electrode and the positive electrode when the battery is assembled.
In such a background, an inorganic solid electrolyte and the like which contain inorganic substance including lithium ion conductive crystals but does not contain organic substance or the electrolytic solution have been investigated and developed (for example, Japanese Unexamined Patent Application Publication Nos. 5-62680 and 2006-185913). In such solid state battery, there is no fear of the liquid leakage and a high temperature heat resistance can be expected such that such solid state battery may be used in a wide temperature range.